Process for preparing nitrogen, carbonic oxide, and hydrogen



Aug. 30, 1932.

COOL [N6 M. E. H. MINOTTE Filed June 21, 1929 Fzesr sceaeaE'E PROCESSFOR PREPARI-NG NITROGEN, CARBONIO OXIDE, AND HYDROGEN 2 Sheets-Sheet 1AMMONIA PUMP WA TER k Mee/so arcas A118 30 1932- M. E. H. MINQTTE1,875,253

PROCESS FOR PREPARING NITROGEN, CARBONIO OXIDE, AND HYDROGEN Filed June2l, 1929 2 Sheets-Sheet 2 caMP/efssaa or @Es/aum. .b 80600 O OOD co/rfavE/v GAS D Ooij UO MAURICE EUGENE HENRI MINOTTE, OE PARIS, FRANCE,ASSIGNOR Patented Aug. 30, 1932 STATES PATENT ortica TO COMPAGNIE DEBETHUNE, E BULLY LES MINES, FRANCE, A CORPORATION OF FRANCE PROCESS IEORPREPARING- NITROGEN, CARBONIC OXIDE, AND HYDROGEN The object of thisinvention is a new and useful process for preparing nitrogen,carbonicfoxide and hydrogen in view of simultaneous synthesis of ammoniaand of methyl alcohol fromv coke oven gases of which the y"following islication.

Persons skilled in theart are aware that coke oven gas is nowadays animportant raw vmaterial in the synthetic ammonia industry. Coke oven gascontains about 50% of hydrogen. AccordingV toV some processes, saidhydrogen is Vdirectly separated from the other gaseous constituents ofthe mixture called coke oven gas through liquefying by adequaterefrigeration of all other gases. According to other processes operationis indirect, steam being decomposed by means of iron at a red heat, and,since iron retains VVoxygen, the kcoke oven gas is used only forreducing the iron oxide produced. y

Persons skilled in the artare also 4aware that, with lsuch processes,serious difficulty ris experienced in obtaining hydrogen in a a true,clear and complete specistate suciently pure ,not to poison cata-"lyzers, the latter being highly sensitive to any traces of unsaturatedhydrocarbons, and, especially, of hydrocarbons of the acetylene typewhichmayarise from coke Booven gas itself.

The same stands true as concerns nitrogen intended to serve forpreparing ammonia. Such nitrogen must be very pure too, and, therefore,the general practice is to prepare -it, through combustion in air ofpart of the ydrogen produced and through condensing the combustionwater, or else through liquefying and distilling atmospheric air.

VVhe-ther nitrogen is obtained by one or the other of said processes,its cost is high owing, in the first case, to the price ofthehydrogenusedY for obtaining it or, in the second case, owing toy theexpenditure required for the air compressing operation and for plantmaintenance;

With either of the processes above referred to for manufacturinghydrogen from Application filed June 21, 1929, Serial No. 372,771, andin France .Tune 27, 1928.

ever, have been partly or totally separatedi for the purpose ofpreparing other products or else for requirements of a technical order.

According to my invention, I have found that `the mixture` of residualgases is, through incomplete combustion conducted under certainconditions, suitable for manufacturing ammonia and methyl alcohol,afterthe required amount of hydrogen has been added thereto.

Complete combustion of the said gases, supposing it were properlyconducted, would obviously produce carbonic acid, water and nitrogen. Itwould then be an easymatter to eliminate the water and the carbonic acidthrough processes well known in the art and nitrogen would remain. Inpractice, however, such a complete combustion is out of the questionbecause of the frequent risk of operating with an excess of air andbecause there would then remain some oxygen mixed with the nitrogenobtained; furthermore, complete combustions are effected at very hightemperatures that foster formation of oxides of nitrogen, whichcompounds are detrimental to later use of the gases obtained.

Incomplete combustion presents no such disadvantages. It has long beenknown that where hydrocarbon gases are burnt in an insufficient quantityof air, the resulting mixture contains nitrogen, carbon monoxide andwater vapor with a little carbonic gas. However, the CO content is toohigh to be used in the synthetic preparation of ammonia and it becomesnecessary to eliminate it, generally, by the action of water vapor uponthe gaseous mixture in the presence of catalysts, or by combustion withan additional supply of air. Whatever the method used, the eliminationof the C() in the form of CO2 is always costly. Inthe process describedhereinafter, the CO kmay be left in its entirety in the gaseous mixture.

My invention utilizes the residual coke oven-gases incident to themanufacture of hydrogen. The object thereof lies in the preparation,under certain conditions, of a ecV Ygas having a high nitrogen content,free from oxidized compounds of nitrogen and nonsaturatedhydrocarbons,but containing from to 15% of CO,/and in the' integral use ef this gasin rthe 'simultaneous syntheses of Vammonia and methyl alcohol. In theinconn- 'plete combustion mentioned above, the hydro# carbons aredecomposed into carbon `andhydrogen under the influence of heat, andeX-v. periments have shown that when vonly part4V of the hydrogen isoi'idized, the whole carbon,

V:on the contrary, is transformedl intoA oxide of carbon, and a smallamountof thisCO is in y turn loxidized topCOvz.

llf no special precautions were taken, traces of nitrogenoxides would befound, though in quantities zwhich would appear less impcrl tant than inthe case of 'complete combustion.

have founditfpossible to preclude the formation of nitrous oxides,during the course of the incompleteV combustion, under vconditions tobe'describedhereinafter, althougg/ fhy there remain immeasurable tracesof'nonsaturated tracesgof hydrocarbons inthe gases,

Y monia, and which it is easy to removeby: dis-'- particularly oftheVacetylene series, which arel also"objectionable in the catalysis of amnvsociationV at high temperature in the presence Y of iron, chromium ornickel filings, or betten.v

of an alloy ofY all three metals.

, "Thee'limination of?the'icarbonicl gas is, .Y brought Yabout in awellv known manner, by i washingVv with ammonia water, on the -cenvtrary, all,` ofthe COremains as it Vwas in ther -35` gasesimmediatelyafterpartial combustion, u so that the cleansing of the gaseous mixtureis very ysimple and consists merelyin the elimination 4ofthewnon-saturated, hydrocarbons and of the carbonic gasi When theycorrecty conditions obtainv under which thegaseous inixturehaving ahigh'nitrogenqcontent'is produced, there -Will be formed nitrogen, hyogen and carben, Hy-V ,dr'ogen is subsequently added in suitableyquantitiesso that the hydrogen content of the 'final 'mixture shall betwice the vcontent and three times the nitrogen content,-in arr- V V`cordance .with the following j proportions:

coeenz:

' The final mixture is then compressed under vapressure'ef900'atmospheres and is led at asuitable ltemperature through a firstcatalyzer causing syntheticl formation' of methyl alcoooe eine mon. f

Afterejondensation and removal of the ,al`` cohol the mixture, stillunderthe same presg sure,jis led Vto the apparatuses wherein syn-ythetic ammonia is produced. i

lt will be seen, therefore, that the synthetic formation ofmethylalcoholjprecedes that of l ammonia, so thaty it'gis unnecessary,inthis" process, to eliminateI all the'CO' contained in v theV refractorymaterial with A-cording to the compositionl of the initial 'gas7 butwillv always be about 4 orr 5% (analysis Y l the mixture transforming itto CO2, and

that all the constituents ofthe mixture [are eventually changed intoValuable products.

l will now describe the process and the plant y 7o for performingthe'same which arethe objects Y of my invention, by referring tothe'sole figure of the drawing appended hereto. Y

and blown v'by' compresser l, is IniXed with ak and the mixturekisinjected into a Ytoweror vgas generator 2, filledl with refractory.material broken" to tiny bits,.andn1aintained at f a high' temperatureby the reaction itself.

The supply rate of the'gaseous mixture is'so ,Ihe residual gas coming 'Yfrom the inanu-V facturmgof hydrogen.. from coke'oven. gas

proper amount of vair blownby compressor 1f,

adjusted that combustion will-*take place without any flaming at the gasgenerator inletv and willV continue chiefly in the interstices of Whichthe latter, is furnished. f I ;Y

The hot gases pass next tower 3 in#V drocarb'ons;A 'Y f l v The VgasesYarethen cooled by means Vof al vtended to destroy all traces ofunsaturated hy- 1 L l I V- y water sprinkling in a scrubber 4, afterwhich 3- theypass into another scrubber 5,'sprinlzled gas.

A pump? circulates the ammonia solution f while'the used solution. isdrained, Yalso con-1 bustion isfcontrolled Vmainly by regulating therelative proportions of gas and of air, and, v' ycorrelativelycentrolling the temperature in- V vside' the Vgas generator. Thistemperature must notbe lower than 1200o C.' at the base of therefractory 'bricks so aste insure dissociation of the whole gas mixture.VOnthe other hand, it must not be higher than i300o i IC. so as notto'jproduce voxide'offnitrogen ywith an.y ammonia solution.ultinfiateiff."`

washing with purified water in a tower 6 dis` v solves the `tracesofammon1a-carr1ed by the1 whichfpass'es througha troughV 8 whereintofY 'lfresh solution is fed 1n a continuous mannerv f Y For thispurpose, wehave but not te'excee'd in l i the gases issuing from the combustiontower f' a maximum kCO2 content, which will Vary ac-V effected aftersteam condensation).

as Vfollows the reaction'should be so conducted V as "to' ob-r Forexample, with an initial ygas composed. Y*

tain at the outlet of the combustion apparatus a gas composed asfollows:

CnHm immeasurable traces CO 11.8 II2 16 CIL 0 N2 l 67.6

' tents through Washings with an ammonia solution and next with puriedWater in order to dissolve the ammonia carried along. The

gases are then fit to be mixed With the hydrogen intended for thesynthesis of methyl alcohol and next of ammonia.

Having now particularly ascertained and described the nature of my saidinvention as `Well as the manner in which the same is to be performed, Ideclare that'vvhat I claim is:

l. A process of obtaining a mixture of nitrogen, hydrogen and carbonmonoxide from residual coke oven gases, which comprises mixing vvith thesaid gases a predetermined amount of air, causing incomplete coinbustionthereof in a gas generator filled With refractory material kept at ahigh temperature, controlling the combustion at a suitable temperatureso as to prevent formation of nitrogen oxides and maintaining the carbondioxide content of the gas mixture at about 4 or 5% by regulating therelative volumes of incoming air and coke oven gases, purifying thegaseous mixture thus obtained by eliminating the traces of non-saturatedhydrocarbons through hot catalytic destruction and by absorbing thecarbon dioxide in awash of ammonia solution, and leaving in the residualgas mixture all of the carbon monoxide Which Was present in the gasgenerator.

2. In a process of simultaneously synthesizing methyl alcohol andammonia from residual `coke oven gases, the steps which comprise mixingwith the said gases a predetermined amount of air, causing incompletecombustion thereof in a gas generator filled With refractory materialkept at a high temperature, controlling the combustion at a suitabletemperature so as to prevent formation of nitrogen oxides andmaintaining the carbon n dioxide content of the gas mixture at about Lor 5% by regulating the relative volumes of incoming air and coke ovengases, purifying the gaseous mixture thus obtained by eliminating thetraces of nonsaturated hydrocarbons through hot catalytic destructionand by absorbing the carbon dioxide in a Wash of ammonia solution, andleaving in the residual gas mixture all of the carbon monoxide Which Waspresent in the gas generator.

In testimony whereof, I affix my signature.

MAURICE EUGENE HENRI MINOTTE.

